A scene from The Man of Mode at the National Theatre. Photograph: Tristram Kenton

'Why can we not always be young and seeing The School for Scandal?" William Hazlitt once asked. Fat chance these days; for, although Sheridan's masterpiece had an outing at the Edinburgh Fringe this year, it is now ignored by the mainstream. But then so is the whole classic comic tradition – admittedly much of it the work of glittering Irishmen – that used to be a vital part of our theatre. We seem, in fact, to be witnessing the slow death of comedy and farce. The upcoming programme of the National Theatre is full of mouthwatering prospects: Middleton's Women Beware Women, Büchner's Danton's Death directed by Michael Grandage, Shakespeare's Hamlet with Rory Kinnear. What is missing is anything likely to raise a laugh. Daniel Evans has also just announced his programme for the reopening of the Sheffield Crucible in 2010. Again, it looks highly promising, with Ibsen's An Enemy of the People, a Sam Shepard revival, a new work by Roy Williams. But classic comedy is conspicuous by its absence.

Why is this? It may, in part, be a sign of our historical amnesia and self-obsession. On the rare occasions when we do revive old comedies, we turn them into reflections on our own society. When Nicholas Hytner directed Etherege's Restoration comedy, The Man of Mode, and Ben Jonson's The Alchemist at the National, he transposed both to modern London rather than treating them as social documents about the past. Much the same thing happened when Jonathan Kent revived Wycherley's uproariously filthy The Country Wife at the Theatre Royal, Haymarket: it became an odd mix of then and now rather than a graphically priapic portrait of the hypocrisy of Restoration London.

I shall doubtless, in asking for period revivals of classic comedy, be accused of wanting "museum theatre". But museums, as we all know, can be exciting places that offer us insights into how our predecessors thought and lived. And, by cutting itself off from our comic inheritance, our theatre is being wilfully self-denying. In the early days of the National Theatre, Bill Gaskill's revival of Farquhar's The Recruiting Officer and Peter Wood's of Congreve's Love for Love banished the whole fan-waving, high-camp approach to Restoration comedy and showed the plays to be riveting social portraits. The tradition of comic acting is also slowly disappearing: one in which buoyancy was often flecked with melancholy. I still cherish the sight of Donald Sinden's features crumpling into despair in a Haymarket revival of The School for Scandal when, as Sir Peter Teazle, he found his supposedly faithless wife hidden behind a screen. Today all that is a distant memory. We seem to have entered a new age of puritanism, when comedy is suspect and its bedmate, farce, severely frowned upon: you should have heard the tut-tutting from many of my colleagues when the Menier Chocolate Factory recently had the temerity to revive Ben Travers' Rookery Nook. Directors are also a pivotal part of the new earnestness. I meet many young applicants to the profession whose sole ambition is to give us new versions of Büchner's Woyzeck, Beckett's Play or Sarah Kane's 4.48 Psychosis. Nothing wrong with any of those pieces. But suggest to young directors that they take a look at Vanbrugh's comedies or Feydeau's farces and they recoil as if one has made an indecent proposal.

Comedy today, in fact, means standup, which bulks large on the Edinburgh Fringe and, increasingly, our West End theatres. While I'm more than ready to tip my hat to such masters of the genre as Ed Byrne or Eddie Izzard, I still pine for periodic revivals of the best work from past centuries. Standup offers us a self-exploratory monologue. Classic comedy presents us with something different: an examination of the greed, gullibility, lust and longing that animated other societies as much as our own. In jettisoning that inheritance, we are denying ourselves serious pleasure.